This invention relates to the manufacture of glass blanks having predetermined outline shapes such as would be used, for example, in the manufacture of window assemblies for automobiles.
In the manufacture of glass shapes for automobile windows and the like it is well known to apply a score line conforming to a desired outline shape to the surface of a rectangular sheet of glass. After scoring the sheet, it is also very well known to apply forces to the sheet so as to cause the glass to break along the score line thereby to enable the marginal edges of the sheet lying outside of the score line to be separated from the remaining glass blank of desired outline contour.
For many years now the above described operations have been carried out automatically on a conveyor line. The rectangular sheets of glass are automatically positioned on the inlet end of the conveyor belt and the conveyor belt is automatically indexed to bring the sheets sequentially to a scoring station and thence to a breakout station wherein the marginal edges of the glass lying outside of the score line are broken off. The glass is then advanced to a further station where the glass blank of desired outline shape is lifted away from the waste marginal portions of the glass (known as cullet). The glass blank is then heated by passing the same through a heating furnace thereby to permit the sheet to be moulded to the desired surface contour.
When the overall configuration of the pattern is generally triangular or the like, a substantial area of glass sheet can be saved if two such patterns can be scored and broken out from a single sheet of glass. This poses no particular problem insofar as the scoring operation is concerned, i.e. two scoring devices can be positioned on the conveyor line each one being arranged to apply a respective one of the score line patterns to the single sheet of glass. The problem arises when an attempt is made to breakout the two patterns which are inscribed on the same glass sheet. It has been found that conventional presses only tend to break the glass around those portions of the score lines which are located toward the marginal edges of the glass sheet. Those portions of the score line patterns which are located toward the central areas of the glass sheet are either not broken at all or are broken in an inconsistent fashion, this problem being particularly acute when there is only a short distance separating the two score line patterns from one another.